   #copyright

Toluene

2007 Schools Wikipedia Selection. Related subjects: Chemical compounds

                               Toluene
                              Toluene
                               General
       Systematic name                                        toluene
           Other names                      methylbenzene
                                            phenylmethane
                                                               toluol
     Molecular formula                                       C[7]H[8]
                SMILES                                      Cc1ccccc1
            Molar mass                                    92.14 g/mol
            Appearance                       Clear, colourless liquid
            CAS number                                     [108-88-3]
                             Properties
     Density and phase                          0.8669 g/cm^3, liquid
   Solubility in water                       0.053 g/100 mL (20-25°C)
           In ethanol,
      acetone, hexane,
       dichloromethane                                 Fully miscible
         Melting point                      −93 °C (180 K)/(-135.4°F)
         Boiling point                   110.6 °C (383.8 K)/ 231.08°F
  Critical temperature                          320 °C (593 K)/ 608°F
             Viscosity                        0.590 c P at 20°C/ 68°F
         Dipole moment                                         0.36 D
                               Hazards
                  MSDS                                  External MSDS
          Main hazards                               highly flammable
              NFPA 704

                       4
                       2
                       0

           Flash point                                  4 °C/ 39.2 °F
             R-phrases                                       R11, R20
             S-phrases                             S16, S25, S29, S33
          RTECS number                                      XS5250000
                       Supplementary data page
Structure & properties                                  n, ε[r], etc.
    Thermodynamic data                                Phase behaviour
                                                   Solid, liquid, gas
         Spectral data                                UV, IR, NMR, MS
                          Related compounds
      Related aromatic
          hydrocarbons                           benzene
                                                 xylene
                                                          naphthalene
     Related compounds                              methylcyclohexane
          Except where noted otherwise, data are given for
                materials in their standard state (at 25°C, 100 kPa)
                                    Infobox disclaimer and references

   Toluene, also known as methylbenzene or phenylmethane is a clear,
   water-insoluble liquid with the typical smell of paint thinners,
   redolent of the sweet smell of the related compound benzene. It is an
   aromatic hydrocarbon that is widely used as an industrial feedstock and
   as a solvent.

History

   The name toluene was derived from the older name toluol that refers to
   tolu balsam, an aromatic extract from the tropical American tree
   Myroxylon balsamum, from which it was first isolated. It was originally
   named by Jöns Jakob Berzelius.

Chemical properties

   Toluene reacts as a normal aromatic hydrocarbon towards electrophilic
   aromatic substitution. The methyl group makes it around 25 times more
   reactive than benzene in such reactions. It undergoes smooth
   sulfonation to give p-toluenesulfonic acid, and chlorination by Cl[2]
   in the presence of FeCl[3] to give ortho and para isomers of
   chlorotoluene. It undergoes nitration to give ortho and para
   nitrotoluene isomers, but if heated it can give dinitrotoluene and
   ultimately the explosive trinitrotoluene (TNT).

   With other reagents the methyl side chain in toluene may react,
   undergoing oxidation. Reaction with potassium permanganate leads to
   benzoic acid, whereas reaction with chromyl chloride leads to
   benzaldehyde ( Etard reaction). Halogenation can be performed under
   free radical conditions. For example, N-bromosuccinimide (NBS) heated
   with toluene in the presence of AIBN leads to benzyl bromide.

   Catalytic hydrogenation of toluene to methylcyclohexane requires a high
   pressure of hydrogen to go to completion, because of the stability of
   the aromatic system

Preparation

   Toluene occurs naturally at low levels in crude oil and is usually
   produced in the processes of making gasoline via a catalytic reformer,
   in an ethylene cracker or making coke from coal. Final separation
   (either via distillation or solvent extraction) takes place in a BTX
   plant.

Uses

   Toluene is a common solvent, able to dissolve: paints, paint thinners,
   many chemical reactants, rubber, printing ink, adhesives (glues),
   lacquers, leather tanners, and disinfectants. It can also be used as a
   fullerene indicator, and is a raw material for toluene diisocyanate
   (used in the manufacture of polyurethane foam), phenol and TNT. Toluene
   can be used as an octane booster in gasoline fuels used in internal
   combustion engines. Toluene at 84% by volume, fueled all the turbo
   Formula 1 teams in the 1980s. Small 1.5L turbo engines were known to
   operate at 5 bar (73 psi) boost in qualifying and 4 bars (59 psi) while
   racing. More than 1500bhp from 1.5L engines was possible. For proper
   atomization, the Toluene fuel blend was preheated. Industrial uses of
   toluene include dealkylation to benzene and disproportionation to a
   mixture of benzene and xylene. Toluene can be used to break open red
   blood cells in order to extract haemoglobin in biochemistry
   experiments.

Toxicology and metabolism

   Inhalation of toluene fumes can be intoxicating, but in larger doses
   nausea-inducing. Chronic or frequent inhalation of toluene over long
   time periods leads to irreversible brain damage. Toluene may enter the
   human system not only through vapour inhalation from the liquid
   evaporation, but also following soil contamination events, where human
   contact with soil, ingestion of contaminated groundwater or soil vapour
   off-gassing can occur.

   The toxicity of toluene can be explained mostly by its metabolism. As
   toluene has very low water solubility, it cannot exit the body via the
   normal routes (urine, feces, or sweat). It must be metabolized in order
   to be excreted. The methyl group of toluene is more easily oxidized by
   cytochrome P450 than the benzene ring. Therefore, in the metabolism of
   toluene, 95% is oxidized to become benzyl alcohol. The toxic
   metabolites are created by the remaining 5% that are ring oxidized to
   epoxides. Most of the epoxides become glutathione conjugated. However,
   the remainder will severely damage cells.
   The metabolism of toluene

   Toluene is mainly excreted as benzoic acid and hippuric acid, both
   formed by further metabolic oxidation of benzyl alcohol.
   The metabolism of benzyl alcohol

Behavioural Effects of Long Term Exposure

   Serious adverse behavioural effects are often associated with toluene
   abuse related to the deliberate inhalation of solvents.^4 Long term
   toluene exposure is often associated with effects such as:
   psychoorganic syndrome;^5 visual evoked potential (VEP) abnormality;^5
   toxic polyneuropathy, cerebellar, cognitive, and pyramidal
   dysfunctions;^5 optic atrophy; and brain lesions.^4

   Toluene causes postural tremors by increasing extracellular
   concentrations of γ-aminobutyric acid ( GABA) within the cerebellar
   cortex.^4 Treatment with GABA agonists such as, benzodiazepines provide
   some relief from toluene induced tremor and ataxia.^4 An alternative to
   drug treatment is vim thalamotomy.^4 The tremors associated with
   toluene misuse do not seem to be a transient symptom, but an
   irreversible and progressive symptom which continues after solvent
   abuse has been discontinued.^4

   There is some evidence that low level toluene exposure may cause
   disruption in the differentiation of astrocyte precursor cells.^6 This
   does not appear to be a major hazard to adults; however, exposure of
   pregnant women to toluene during critical stages of fetal development
   could cause serious disruption to neuronal development.^6

   Retrieved from " http://en.wikipedia.org/wiki/Toluene"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
